Conventional rolling shutters typically include an array of horizontal slats which are articulated or linked such that the shutter can be rolled or wound onto a storage roller. Storage roller drive mechanisms are used to rotate the storage roller in opposite directions to roll and unroll the shutter between shutter-open and shutter-closed positions. As the shutter slats are fed off the storage roller, opposite ends thereof are received and guided in side rails secured exteriorly to the side of a building at respective sides of the building opening being secured by the rolling shutter, such building opening usually including a window or door. The side rails usually are linear and retain the shutter slats in generally coplanar relationship parallel to the plane of the opening.
When retrofitting an existing building with a rolling shutter, common practice has been to mount the storage roller exteriorly of the building with a valance being provided to hide the rolled-up shutter from view. Prior valances or housing covers have been made of metal and have had a box-like appearance that was not particularly aesthetically pleasing.
In order to open and close the shutter from inside the building, an operator or controller such as a strap, crank or chain was provided inside the building and connected through the wall to the storage roller. This usually required the drilling of a hole through the wall to accommodate the element or elements coupling the operator inside the building wall to the drive components located outside the building wall.
One known type of storage roller drive mechanism used a crank as the interior operator. The crank was connected by a universal joint to the inside end of an axle which extended through a hole in the wall for inline connection to a worm. The worm was in mesh with a worm gear attached to the storage roller whereby rotation of the crank in one direction would raise the shutter and rotation in the opposite direction would lower the shutter. Although a bi-directional drive mechanism is desirable, one problem encountered with the foregoing type of crank drive mechanism was the need, during installation of the rolling shutter system, to drill the axle hole with a high degree of precision or make the hole excessively large in diameter to assure proper alignment of the shaft with the worm and a universal joint support secured to the side wall of the building. This generally discouraged installation of the rolling shutter system by individuals other than professional installers who had the proper tools and skill. Accordingly, such systems were not particularly suited for installation by the do-it yourself home owner.
The foregoing crank operated drive mechanism desirably was self-locking to prevent the rolling shutter from lowering by reason of its own weight. The self-locking feature, however, was heretofore provided at the cost of efficiency. Because of the inefficiency of the drive mechanism, whether raising or lowering the shutter, a high mechanical advantage (high gear ratio) was needed to keep operating force low. An undesirable consequence of this was that a large number of crank turns were needed to raise and lower the shutter. Even though the crank was easy to turn, the large number of needed crank turns made raising or lowering of the shutter a slow and somewhat tiresome task. Moreover, turning of the crank was a relatively unnatural human movement.
Narrow straps with retractor mechanisms also have been used. Generally, one end of the strap would be wound onto a large diameter drum coupled to the shutter storage roller outside of the building. From the drum, the strap would pass through a hole in the wall to a pulley mounted at the inside surface of the wall which directed the strap downwardly to a retractor mechanism also mounted to the inside surface of the wall. To raise the shutter one would pull down on the strap in a more natural human movement aided by gravity. When the strap was released, the retractor mechanism would engage to prevent reverse movement of the strap. To lower the shutter, the strap was pulled away from the wall to release a length of the strap from the retractor mechanism and then allowed to move back towards the wall to allow the shutter to lower by its own weight a distance determined by the length of strap released by the retractor mechanism. This procedure was relatively awkward and had to be repeated many times to completely lower the shutter from its fully raised position. Another problem has been that if the retractor mechanism should fail or the strap break, the shutter could crash down by reason of its own weight. Also, the strap had to be gripped tightly to prevent the strap from slipping in the operator's hand. Accordingly, persons with weak grips have had difficulty with strap operated shutter systems.
Another problem associated with indirect drive systems, i.e., those systems that rely solely on gravity to lower the rolling shutter, was that when the shutter stuck in an open position, one had to reach out through the building opening to pull the shutter down at least to get lowering movement started. Moreover, the shutter more likely would stick in the usually more difficult to reach fully raised position when gravity forces acting to lower the shutter are the lowest.
Another problem associated with bi-directional drive mechanisms, whether operated with a crank or otherwise, has been damage to the system when attempting to lower the shutter too far or when stuck.
Known rolling shutters also have been provided with a mechanism to prevent the shutters from being raised from the outside when in their fully closed position. A common approach has been to use straps to connect the top slat of the shutter to the storage roller. When one attempted to raise the shutter from the outside, the uppermost shutter slat could move relative to the storage roller for jamming against the top wall of the shutter housing or valance. Nevertheless, the shutter could still be lifted somewhat until the jamming occurred. Also, it is more desirable in bi-directional drive systems to directly connect the rolling shutter to the storage roller for more positive driving of the rolling shutter.